Names of places and highland attire

[McClef]

alumna - alumnae

Is it not Alumnus? I am an Alumnus of the University of St Andrews and they think it is.

This is like Attornies General and Surgeons General

That said, I totally agree that the best choice is to use the plural found in the native language, and I totally agree with the point you made with the Latin/Hebrew/Inuit. Unless of course the plural in the native-language is so unknown by English speakers that you're the only one using it, because in "proper" language a lot of times majority rules; if you're the only one using the Gaelic plural, then it will be hard for that to win out over the English plural.

To have Attorney Generals or Surgeon Generals would seem to indicated a senior military man practising law or surgical operations.

But yes, there is the problem where there are not many speakers of a language around that the word may be imported into English but then be made subject to English rules. All or most English speakers will know what an Eisteddfod is but they probably wont pronounce the singular correct (not remembering to pronounce the single f as a v) but will pluralise by adding an s instead if the correct au. And the Brits and the Americans can not always agree on words in the first place!